A decision that could wipe out the most serious charges against a Pembroke dentist on trial on counts including drunk driving causing death is now in the hands of a judge.

The long-running trial of Dr. Christy Natsis is on another lengthy hiatus while Ontario Court Justice Neil Kozloff considers arguments by the dentist’s lawyers that the work of the three Ontario Provincial Police collision investigators who probed the crash is too biased to be considered reliable expert opinion evidence.

As such, the defence argues, the investigators’ calculations and conclusions about what happened in the moments leading up to the March 31, 2011, crash that killed Bryan Casey is so flawed that it shouldn’t be allowed into evidence against Natsis.

But the Crown argued that excluding the police reports into what they believed happened that night on Highway 17 near Arnprior would be “drastic and unprecedented.”

“Innuendo, highly selective interpretation and exaggeration are no substitute for evidence,” according to the Crown.

The stakes are high: If the defence is successful at having the evidence excluded, it would gut the prosecution’s case on the charges of impaired driving and dangerous driving causing death against Natsis. If that happened, it would leave the Crown with the possibility of securing little more than a conviction on a simple impaired driving charge, which carries a minimum $1,000 fine, no minimum jail time and a one-year licence suspension. A person convicted of the more serious offences could be looking at a prison sentence of between two and five years.

Natsis’s team of lawyers — made up of Michael Edelson, and partners Vince Clifford and Solomon Friedman — argue Kozloff has little choice but to exclude the evidence. They argue it is the product of biased investigators whose work was tainted by their desire to secure a conviction for the Crown. They were not independent experts who let science inform their opinions, the defence argues.

The defence cites several problems with the evidence of investigators Shawn Kelly, Jeffrey Hewitt and their supervisor, Robert Kern.

Among them:

That Kelly and Hewitt worked too closely with the investigating officer;

That Kelly injected himself into the investigation, musing about a possible legal defence;

That Kelly subjectively selected relevant evidence and excluded or destroyed other evidence from the crash scene;

That draft copies of all the reports existed but were deleted; and

In the opinion of the defence, the reports of Kelly and Hewitt are “infected with the twin viruses of tunnel vision and confirmation bias.”

“There is no single case in the jurisprudence with such an overwhelming evidentiary record of bias, partiality, lack of independence, lack of credibility and utter unreliability,” wrote the defence. “The only possible remedy that could address the fatal flaws in the proposed experts’ qualifications is the exclusion of their evidence.”

The Crown argued the “highly skilled and well trained” officers conducted themselves professionally.

“The body of evidence before the court does not support the exclusion of any, let alone all, of their evidence. They are not biased. They are sufficiently independent. They are not partial. Their conclusions are supported by the documented physical evidence,” the Crown wrote.

The alleged frailties in the testimony of the officers is only something the judge should consider when he determines a verdict at the end of the trial, according to the prosecution.

The trial, which began in November 2012, has already seen critical evidence against Natsis excluded because of police mistakes. Breath samples that showed a blood-alcohol level nearly 2 1/2 half times the legal limit were tossed after the judge concluded the arresting OPP officer violated Natsis’s rights by repeatedly interrupting a phone call to her lawyer. The officer, OPP Const. Ryan Besner, eventually took the phone from Natsis and hung up on the lawyer.

Casey, an engineer at a Siemens Canada project at Chalk River, was on his way home to his wife and three children when, it’s alleged, Natsis crossed the centre line and hit him. Casey, who himself had a blood-alcohol level over the legal limit, went into cardiac arrest en route to the hospital.

His widow, LeeEllen Carroll, and father, William (Gus) Casey, have sat in on nearly every minute of Natsis’s trial, which is now not expected to resume until October.